Based On NMDAR1 Signaling Pathway, The Effects Of Tianxiang Capsule On Vestibular Nucleus Excitability In Rats With Motion Sickness Were Investigated

Motion sickness is an acute syndrome caused by abnormal acceleration stimulation when people are travelling by car,ship or plane,and its main manifestations are dizziness,nausea,vomiting,pallor,fatigue and so on.A large number of studies have shown that vestibular system plays an important role in the occurrence of motion sickness.And the excitability of vestibular nucleus activated by peripheral vestibular afferent is a key link in the pathological process of motion sickness.Previous studies have shown that glutamate is the major excitatory neurotransmitter in vestibular nucleus neurons and NMDAR1 signaling pathway is activated when motion sickness occurs.And the activation of NMDAR1 downstream signal factor CaMKIIa and CREB can further induce the expression of c-fos gene.In recent years,numerous studies have been confimed that c-fos protein can be used as a marker for activation or excitation of vestibular nuclear neurons and its expression level could reflect the activity state of vestibular nucleus neurons.At present,anti-motion drugs are mainly western medicine preparations,although the beneficial effect has been shown,there are obvious side effects.Traditional Chinese medicine(TCM)has unique advantages in the prevention and treatment of motion sickness.Our research group developed Tianxiang capsule according to TCM theory.Tianxiang capsule is a prescription based on the clinical practice of long-term treatment of motion sickness and innovation of TCM pathogenesis of motion sicknes's.It is proved that Tianxiang capsule has a good effect in the prevention and treatment of motion sickness in preliminary clinical application,but the pharmacological mechanism is not completely clear.Therefore,the motion sickness rats model was established by biaxial rotation stimulus,and the present study was designed to investigate the effects of Tianxiang capsule on the behavior of rats with motion sickness,c-fos expression and NMDAR1 signaling pathway in the vestibule nucleus of rats with motion sickness.The aim of this study was to verify Tianxiang capsule efficacy and identify its targets of anti-motion sickness effects,which could lay a foundation for developing a new clinical anti-motion drug in the future.Objective:The aim of this study was to verify the anti-motion efficacy of Tianxiang capsule by investigating the effects of Tianxiang capsule on the behavior of rats with motion sickness.Meanwhile,the molecular mechanism of Tianxiang capsule regulating the excitability of vestibular nucleus was explored by investigating the effects of Tianxiang capsule on c-fos expression and NMDAR1 signaling pathway in the vestibule nucleus of rats with motion sickness,which could partly interpret the underlying mechanism of Tianxiang capsule action in depth and provide further experimental evidence for NMDAR1 signaling pathway was involved in the excitability of vestibular nucleus in motion sickness.Methods:1.The effects of Tianxiang capsule on the behavior of rats with motion sickness were observed:the SD rats were randomly divided into six groups,including normal group,model group,scopolamine group,low-dose,mid-dose and high-dose Tianxiang capsule groups.The drugs were intragastrically administrated for 3 days,and then the rats motion sickness modelwas induced by biaxial rotation stimulus.The behavioral changes of rats were evaluated by the motion sickness index,the spontaneous activity test and Kaolin pica,to verify the efficacy of Tianxiang capsule.2.The effects of Tianxiang capsule on c-fos expression in the vestibule nucleus of rats with motion sickness were observed:the experimental grouping and processing were the same as above.The expression of c-fos in the vestibule nucleus of rats was detected by Elisa,Western Blotting and Immunohistochemistry,to investigate the effects of Tianxiang capsule on c-fos expression and reveal the regulating effect of tianxiang capsule on the excitability of vestibular nucleus in rats with motion sickness.3.The effects of Tianxiang capsule on NMDAR1 signaling pathway in the vestibule nucleus of rats with motion sickness were observed:the experimental grouping and processing were the same as above.The expression of NMDAR1 and the phosphorylation level of CaMK?? and CREB in the vestibule nucleus of rats in each group was detected by Western Blotting,which could investigate the effects of Tianxiang capsule on NMDAR1 signaling pathway to reveal the molecular mechanism of the regulating effect of tianxiang capsule on the excitability of vestibular nucleus in rats with motion sickness.Results:1.Tianxiang capsule effectively improved the behavioral changes of rats with motion sickness:Compared with the normal group,the motion sickness index,the number of fecal granule and Kaolin intake were significantly increased(P<0.01),total traveling distance and frequency were significantly decreased(P<0.01)in the model group,which suggested that the rotation stimulus could induce common symptoms of the motion sickness.Compared with the model group,the motion sickness index and Kaolin intake were decreased(P<0.01,P<0.05),spontaneous activity was increased(P<0.01 P<0.05)in mid-dose and high-dose Tianxiang capsule groups,suggesting that Tianxiang capsule has certain effect on motion sickness.2.Tianxiang capsule can inhibit the excitability of vestibular nucleus of rats with motion sickness:Compared with the normal group,the c-fos expression was up-regulated significantly(P<0.01)in the model group with statistical difference,which indicates that the enhancement of the excitability of vestibular nucleus.Meanwhile,it was confirmed again that the hyperexcitability of vestibular nucleus was involved in the pathological process of motion sickness in rats.Compared with the model group,the c-fos expression was down-regulated significantly(P<0.01,P<0.05)in Tianxiang capsule groups,which indicated that Tianxiang capsule may play its good effect on motion sickness by regulating the excitability of the vestibular nucleus.3.Tianxiang capsule can inhibit NMDAR1 signaling pathway in the vestibule nucleus of rats with motion sickness:Compared with the normal group,the expression of NMDAR1 and the phosphorylation of CaMK?? and CREB were up-regulated significantly(P<0.01)in the model group,which suggests that NMDAR1 signaling pathway was activated in motion sickness and participated in the pathological process of vestibular nucleus excitability in motion sickness.Compared with the model group,NMDAR1 signaling pathway was significantly inhibited(P<0-01,P<0.05)in mid-dose and high-dose Tianxiang capsule groups.It is indicated that Tianxiang capsule may play its good effect on motion sickness via regulating the excitability of the vestibular nucleus by inhibiting NMDAR1 signaling pathway.Conclusion:1.Tianxiang capsule showed good effects on motion sickness by effectively improving the behavioral changes of rats with motion sickness.2.Tianxiang capsule could reduce the expression of c-fos protein in the vest:ibule nucleus of rats with motion sickness,suggesting the anti-motion effect of Tianxiang capsule might be related to the down-regulation of the excitability of vestibular nucleus.3.Tianxiang capsule could down-regulate the expression of NMDAR1?P-CaMK???P-CREB protein and inhibit NMDAR1 signaling pathway in the vestibule nucleus of rats with motion sickness.This may be one of the pharmacological mechanisms of Tianxiang capsule for inhibiting the excitability of vestibular nucleus in the treatment of motion sickness.